Thread (27 messages) 27 messages, 7 authors, 2012-09-08
STALE5017d

[PATCH] ARM: formalize an IPI for CPU wake-ups

From: Kukjin Kim <hidden>
Date: 2012-08-08 10:39:22

Colin Cross wrote:
On Wed, Aug 1, 2012 at 2:42 AM, Kukjin Kim [off-list ref] wrote:
quoted
Stephen Boyd wrote:
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On 07/10/12 23:34, Kukjin Kim wrote:
quoted
Stephen Boyd wrote:
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Great. Kukjin Kim, can exynos use SGI0? It looks like exynos is the
only
quoted
quoted
one left to move to SGI0.
Yeah, EXYNOS can use SGI0 instead of SGI1 :)
Russell, can we apply something like this?
Please feel free to add my ack on following change.

Acked-by: Kukjin Kim <redacted>
When testing coupled cpuidle on Exynos5, I found that sending an IPI
does not successfully wake up CPU1.  CPU1 is in a wfe with interrupts
masked, not a wfi, so an interrupt is not able to wake it up.  It
tends to wake up anyways because the next time a spin lock is
unlocked, often during a timer interrupt on CPU0, CPU0 executes an sev
which wakes up CPU1.  You can see that the IPI is unnecessary by
removing the gic_raise_softirq and replacing it with dsb_sev().
Hmm...could be. Let me check you commented in detail. And if any updates,
I'll let you know.

Thanks for your information.

Best regards,
Kgene.
--
Kukjin Kim [off-list ref], Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.
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